I bought Toyota Yaris Hybrid in 2012. Toyota at that time claimed it should be 4.4 l/100. My average after 4 years before I sold it was 5.1. So my usage was just 15% off. And this was in Norway with a lot of driving in mountains.

On the other hand with electrical cars that I rented and from what I heard from friends the real range was shorter by 20% or more.